Electrochemical performance of sol-gel-made Na2Ti3O7 anode material for Na-ion batteries.

Nanocrystalline Na2Ti3O7 material is prepared by a newly developed sol-gel procedure. The sol-gel made Na2Ti3O7 calcined at 500 °C possesses mesoporous structure and BET surface area of 89 m2 g−1. X-ray diffraction and scanning electron microscopy confirm the presence of sintered nanosheets or very small crystals of the size of 10-20 nm with short-range ordering. Electrochemical behavior of nanocrystalline Na2Ti3O7 is evaluated by cyclic voltammetry of Na insertion and by galvanostatic chronopotentiometry at different charging rates. The sol-gel made Na2Ti3O7 exhibits improved performance as compared to that of the microcrystalline Na2Ti3O7 prepared by solid-state synthesis. Discharge capacities of optimized material at charging rates 1, 2, and 5C reach 109, 86, and 63 mAh g−1, respectively, with 100% coulombic efficiency and zero capacity drop over 50 cycles after initial conditioning. Excellent performance of Na2Ti3O7_500 is obviously an effect of its large surface area giving rise to predominantly capacitive mechanism of charge storage. Hence, sol-gel made nanocrystalline Na2Ti3O7 represents promising anode material for Na-ion batteries due to its charge capacity and outstanding cycling stability.ᅟ<graphic></graphic> [ABSTRACT FROM AUTHOR]